Test Research On AO-type Land Biological Filter Wastewater Treatment System

In recent years, with economic of the small towns and villagesprospering and developing, the environmental problems of it arebecoming increasingly serious, and thus it’s urgent to find a wastewatertreatment process, which, with low infrastructure and operation cost,better treatment effect, simple operation and maintenance, is suitable forthe application of small towns and villages.To this end, the biological aerated filtration wastewater landtreatment system was developed and studied. Through the test, the effectof COD volume load and feeding mode （up-flow and down-flow） onCOD and NH₄⁺-N removal in synthetic wastewater was studied, andthrough the flowing pattern test, the reactor type of the biological aeratedfiltration wastewater land treatment system under the same conditionswas studied. The results showed that: in the flow of60L/d and theaeration rate of0.48L/min, with gravel as the media, the biologicalaerated filtration wastewater land treatment system can both removeCOD and NH₄⁺-N at the same time; the differences of COD removalefficiency between the up-flow and down-flow biological aeratedfiltration wastewater land treatment systems were negative and the highest COD removal efficiencies,96%and97%separately, were bothachieved when the COD volume load was in0.089kgCOD/（m³d）; theremoval efficiency of NH₄⁺-N decreased with the COD volume loadincreasing by the biological aerated filtration wastewater land treatmentsystem，and the removal efficiency of down-flow system was higher thanthat of the up-flow, about11.1%²8.3%. The flowing pattern test, withRhodamine B as a pulse tracer, showed that both the up-flow anddown-flow land treatment systems are completely mixed reactor.In order to enhance the removal of TN, the AO-type land biologicalfilter wastewater treatment system was developed and studied on thebasis of the test research on the biological aerated filtration wastewaterland treatment system. Through the test, the effect of COD volume loadin the aerobic zone, reflux ratio and temperature on the removal of eachpollutant were studied, and with the analysis of the wastewater quality onvarious pollutants along the way, the region of the contaminants removalwas studied and the reaction type of the aerobic filtration column wasconfirmed. The results showed that: in the AO-type land biological filterwastewater treatment system, at a temperature of25.3²6.7℃, a refluxratio of100%, the removal efficiency of COD, NH₄⁺-N, TP, TN decreasedwith the COD volume load increasing; the effect of the COD volume loadon COD removal was negative at the volume load of0.025⁰.110 kgCOD/（m³d）, and the effluent COD of the system reached an Aemission standard; the effluent NH₄⁺-N of the system reached an Aemission standard when the COD volume load was not greater than0.087kgCOD/（m³d）; the system’s TP removal efficiency was poor. Theremoval efficiency of each pollutant in the AO-type land biological filterwastewater treatment system increased with the temperature increasingwhen it ranged from12.0℃to26.7℃, at a reflux ratio of100%, withthe volume load ranging from0.048kgCOD/（m³d） to0.057kgCOD/（m³d）; the influence of temperature on NH₄⁺-N, TN removal waspretty obvious, and when the temperature above15℃, the system’seffluent NH₄⁺-N reached an A emission standard. Under the conditions of16²0.5℃and40L/d, the influence of reflux ratio on the nitrificationwas unconspicuous, while on the denitrification was much obvious; whenthe reflux ratio ranged from100%to300%, the TN removal rateincreased from58.7%to72.0%, and in the reflux ratio of300%, theeffluent TN dropped to13.9mg/L, achieved an A emission standard; andTP removal efficiency increased with the reflux ratio decreasing. Most ofthe COD and TN removal occurred in the anaerobic zone, whilenitrification and further removal of COD happened in the aerobic zone,and the two aerobic filter columns were completely mixed reactors.The test research provided a certain criterion of parameters support for the AO-type biological filter wastewater land treatment system used inthe actual project and had a realistic significance to select and apply awastewater treatment process for small towns and villages.